Glass composition and product thereof



Patented 1 3,

cuss courosrnon m mum I n'rnsasor y Harold a. Moulton, swim-le mas, assignor Etc American Optical iMasa, a

Company. sonihbrl s voluntary association of Massachum Drawing. Application August 4,1941,

' Serial No. 405.873

5 Claims. (Cl. roe-41) This invention relates to a novel vitreous or glass composition and method of making the same i and also to articles of said composition.

A principal object of the invention is to provide a vitreous or. glass composition and method of making the same having the properties of high index of refraction, high reciprocal relative dispersion, low fusing point, freedom from color, and possessing characteristics particularly adaptable to forming optical products.

Another object is to provide a vitreous or glass composition having the. above characteristics which will be relatively stable to weathering.

Another object is to provide a stablized cadmium borate glass composition and/or lensesof said composition.

.Other objects and advantages of the invention will become apparentfrom the following descriptionjand it will be seen thatjmany changes may be made in the arrangements of ingredients and methods described withoutdeparting from the spirit of the invention as expressed in the aceompanying claims. I, therefore, do not wish to be limited to the exact details and methods described, as the preferred forms only have bee set forth by way of illustration. I

Glasses having relatively high index of refraction and high reciprocal relative dispersion, with low fusing point, have been known in the past, but such glasses in most instances have been unstable as to "weathering," corrosion, etc., and were not of a desirable commercial nature, particularly for use in forming ophthalmic lenses.

It, therefore, is one of the primary objects of this invention to provide glass composition and .method of making the same having the desired properties of high index of refraction, high reciprocal relative dispersion, and low fusing point, and which will be stable to weathering" and corrosion and desirable for use in forming ophthalmic lenses.

The priorart, as far as is known, makes no mention whatsoever of any glass making use of of embodying the invention comprises'preferably the following ingredients:

, Percent CdO (cadmium oxide) ..50-to 80 B: (boric anhydrideL- 20 to 50 BeCOa (beryllium carbonate) 5 r020 together with minor quantitiesof ingredients which promote fusion characteristics of the mixture, such as alumina,;alkali compounds, alkali earth compoundsand arsenic, antimony or bismuth compounds. It is to be understood that these minor ingredients will be used in accordancewith the known art in other glasses and in proportions for producing a desirable resultfor this new and novel glass composition in which knowledge of the prior art is only a primary guide.

If desired, all or part of the BeCOs (beryllium carbonate) maybe replaced by A120: (aluminum oxide) to modify the coefficient' of thermal ex-' pansion, to change the partial dispersion and to modify the stability under certain conditions." It will be understood that other 'berylliur nfonaluminum compounds may be selected from a group consisting of B8804 Be(OH)z (beryllium hydroxide), Be'SiOs (beryllium silicate) A120: (aluminum oxide),' BeO (beryllium oxide) ARCH): (aluminum hydroxide), AlPOt (aluminum phosphate),etc.

The foregoing compositionwill be moretransparent than ordinary glass of the same index to light of low wave length and articles formed thereof will therefore possess this desirable feature as well as those set forth above as regards resistance to corrosion and weathering."

It has been found that a more colorless transparent glass can be made by incorporation of the the chemical element known as cadmium. The

use of such an element, without going in research, would not be obvious. The oxide of the element being of a brownish color would not appear promising as a glass making ingredient. Applicant has found, however, that the incorporation of cadmium oxides in glass compositions of suitable character will produce clear, sparkling, white glass having high indices of refraction and high reciprocal relative dispersion of a novel and useful character. The composition or product therestabilizing ingredients in metallic form preferably mixed with the batch. This is due tojthe reducing action of these metals on tracesofximpurities which may be present more specifically iron. It, therefore, is to be understood thatthis incorporation of stabilizing ingredients in metal licform is a feature of this invention.

It is to be understood that all percentages of the various ingredients used are figured on the basis of the complete batch. i It is also to be understood that if desiredfa composition having the above characteristics may 'v have incorporated in it, elements producing ab-.'

sorption in the visible or invisible regionsof the spectrum. Such elements, for example, might be as follows:

(beryllium sulphate) Cerium compounds toproduce absorption beginninginthenearultraviolet.

sen-om iron to give pronounced absorption in the infra-red, or compoimds incorporating both of the above ingredients. might be used to give.

a sharp cut-oi! at either end of the visible spectrum. Other well known coloring oxides, such as cobalt, nickel, etc. may be also added for producing selected absorptions in the visible region or the spectrum.

The compositions produced by the above formulae are preferably used herein as the bodypor tion of ophthalmic lenses. The required finished optical surfaces of the. lens are Ienerated on the body portion byabrading tools and machines 1 suchasarecommonlyusedlntheartandare carefully formed to the prescriptive requirements The glass analyses given in the following claims I are expressed as oxides as is customary. It is to be understood that these analyses areto include the use of other equivalent chemical expressions of the elements which are familiarfto those skilled in the art as for example CdO 1. A vitreous composition whose is expressed as: 7

Per cent Cadmium oxide 50 to 80 Borg anhydride to 50 and a stabilizer introducing beryllium. based on the batch.

from 0.5 to 2.5%

2. A'vitreous composition whose analysis is expressed as:

' Per cent Cadmium oxide 50 to 80 Boric anhydride 20 to 50 a stabilizer introducing from 2.5 to 10% aluminum, based in the batch.

3. A vitreous composition whose analysis is expressed as:

Per cent CdO 50 to 80 20 B20: 20 to 50 (cadmium oxide) might be expressed as CdCOs,

Cd(NO=) etc. The analyses given in the claims. therefore, are intended to cover all of such equivalent chemical expressions.

From the foregoing description it will be seen that novel means and method have been provided for obtaining a high index, high reciprocal relative dispersion vitreous composition, or product thereof, having a relatively low fusing point and which will be more stable to weathering," corrosion, etc.

Having described my invention, I claim:

1a compound selected from a group consisting of beryllium compounds and aluminum compounds,

Per cent FeO 0 to 10- and C80: 0 to 5 4. A vitreous composition whose analysis is expressed as:

Per cent Cadmium oxide to- .Boric anhydride 20 to 50 and material selected from a group consisting of beryllium compounds and aluminum compounds and mixtures of said compounds.

5. A lens comprising a body portion formed of a material of a vitreous composition whose analysis is expressed as:

4 Per cent 4 Cadmium oxide 50 to 80 Boric anhydride 20 to 50 and from 0.5 to 10% of a material selected from a group. consisting of beryllium compounds'and 45 aluminum compounds and mixtures of said compounds.

HAROLD R. MOULTON. 

